This grant deals with attempts to chemically define the relationship between the structure and function of chromatin in eukaryotic cells, and contains the following major projects which are in progress: 1. Purification of the nuclear histone acetylase from calf thymus. 2. Substrate selection by the purified histone acetylase enzyme. 3. The mechanism of action of n-butyrate in increasing histone acetylation. 4. Characterization of nucleosome-like particles formed between histones and single stranded DNA. 5. An electron microscopic investigation of altered chromatin structure in active genes.